Method of treating bristles and product thereof



Jan. 19, 1943. STONE-LL 2,309,021

METHOD OF TREATING BRISTLES AND PRODUCT THEREOF Filed July 16, 1938 F .1. fl BR/STLES TREATED WITH FURMALDEHYDE soLur/olv BUNDLE 0F BR/sTLE-s /MMER SED m WATER THE/v lMMERSED FOR 24 HOURS /N FORMALUEHYDE BATH sPEc/AL LY ADJUSTED TREATED BUNDLE R/NsEn WITH WATER PRELIMINARY DRY/N6 BY CENTR/FUG/NG FINAL DRY/N6 BY HANGING BUNDLES o/v RACK IN VEN TOR. ALBER T A. JTQNEH/Lz.

BY f We Patented Jan. 19, 1943 METHOD OF TREATING BBISTLES AND PRODUCT THEREOF Albert A. Stonehlll, Brooklyn, N. 1., assignor to Brunswl Johnson .& Johnson, New

corporation of New Jersey I Application July 10, ms, Serial No. 219,664

4Clalms.

The invention relates to the treatment of bristles mainly intended for use in brushes under wet service conditions, for example, toothbrushes and other personal use brushes as well as paint and the like brushes. 7 Principal objects are to provide for strengthening the bristles, regardless of their source, and greatly to prolong the useful life of brush bristles by making them highly resistant to wet breakdown and to accomplish these results without impairing the natural flexible stiflness of the bristles or, in short, without danger of embrittling the bristles.

The problem of wet breakdown of brush bristles has had considerable attention and many so-called waterproof treatments have been proposed. "Wet breakdown is to be understood to mean that the bristle is hydrolyzed by water and/or, for example, in the case of toothbrushes, the chemical action of the multifarious dentifrices in the form of liquids, powders, pastes and creams, with the result that the bristles become soggy and therefore lifeless. A lifeless bristle exerts no beneficial brushing action. The methods of treatment heretofore projected have proceeded upon the principle of arming the bristle so as to enable it successfully to cope with such wet breakdown conditions. Otherwise stated, the methods heretofore projected contemplated the addition to the bristle of substances either in the guise of impregnants or as coatings.

In many instances the cure was worse than the ill in the sense that untreated bristles not infrequently showed better results under test than treated bristles of the same class. The effect of some treatments was a condition akin to marked embrittlement which caused the bristle to snap when subjected to slight deflection or to split in the direction of its length; lninstances where coatings were employed the coatings wore away and left exposed the original bristle body with the result that wet breakdown took place; where impregnants were used, they were subject to removal by the solvent action of the dentifrice; the effect of other treatments was to destroy the inherent flexible stiffness and to render the bristle soft and soggy with a pronounced tendency to flare out at the ends and to mat. In any event, the conditions stated are definitely acute in the case of toothbrushes for the reason that loose and broken bristles and soggy bristles, resulting from wet breakdown, or from subsequent breakdown of the protective coatings or impregnants of the prior art, are a decided menace to health and comfort. f s

Having in mind that untreated bristles of a certain group or glass frequently tested out better than bristles of the same group impregnated and/or coated according to methods heretofore projected, I centered my efforts on studies as to just what constituted the natural strength of the bristle, when measured in terms of flexible stiffness, and as to whether or not I could add to the natural strength and also prolong the useful life of the bristle. After extended study and research, I discovered that I could produce a superior bristle, that is to say, a bristle possessed of added strength and a high order of efiiciency over long periods of wet service by departing from the methods and practices heretofore projected and utilizing a novel treatment of the bristles.

Nitrogeneous materials enter into the constitution of almost all bristles, the principal component being a protein substance known as keratin which is readily attacked by alkalis and easily hydrolized by them. My invention is predicated on these facts and its nature consists in effecting a chemical modification of the bristle structure by reacting the keratin with an aldehyde under such conditions as to impart great strength to the bristle and make it more resistant to wet breakdown.

Fi 1 is a side view of a tooth brush in which the bristles of the present invention may be used; and

Fig. 2 is a diagrammatic illustration of the steps employed to treat said bristles.

More specifically stated the invention in one aspect consists in treating bristles with an aldehyde solution, and preferably formaldehyde in solution at a pH value below '7. I have found that when bristles are treated with a formaldehyde solution at a pH value above 7, they are not appreciably strengthened and, in fact, showed no appreciable resistance to wet breakdown. I attribute this to the fact that the hydrolizing effect of the alkali on the keratin had already been exerted before the formaldehyde was able to exercise its toughening action.

In the practice of the invention a batch of bristles, in the original uncut bundles, is immersed in water, preferably distilled water, afterremoving the retaining bands and flaring out the butt ends to prepare them for the toughening and/or hardening treatment. After. an interval of about fifteen minutes or for such time as to enable the bristles to become thoroughly soaked, the bundles are removed from the water, relieved of excess -moisture and placed in perforated trays. The

lowered into a tank containing a formaldehyde bath and are allowed to remain submerged for the required time which sometimes reaches a period of twenty-two hours.

The bath is a 20% solution of formaldehyde 5 obtained by adding to the commercial 40% solution of formaldehyde an equal quantity of water. The solution is adjusted to a pH value below 7, the preferred pH range being between 3.5 and 4.5. The adjustment may be made by the addition of tenth normal sodium hydroxide or tenth normal sulphuric acid, according to the requirements of the solution.

After the required lapse of time for the toughening treatment, the formaldehyde solution is drained off and replaced with water whereupon the tank is again drained. Thereafter the trays are removed from the tank and the bundles of bristles are subjected to the action of a centrifugal drying machine after first applying elastic webbing garters to the butt ends of the bundles in order to prevent curling of the bristles during drying. Drying by the centrifuge is preferably limited to one-half hour more or less, final drying being completed in appropriate drying racks. After this the garters are removed and replaced by elastic bands applied to the butt ends of the bristles to prevent curling under storage conditions.

Examples of baths that have proved eminently satisfactory in so chemically modifying brush bristles as greatly to increase the wet strength thereof, are as follows:

40% solution of formaldehyde pounds 40 Water (in 34, 10% sodium hydroxide solution (solution adjusted to pH 3.6) cc 10 40% solution of formaldehyde pounds Toothbrushes made from bristles treated in the above manner have been found to retain their toughness even after artificially ageing at a temperature of F. continuously for more 55 than six months.

The efiect of my treatment of bristles is somewhat akin to the efiect of tanning on hides and skins. It does not make them water repellent and they do not shed water but actually, as is desirable in service, hold water like untreated bristles.

The chemical efiect of the treatment, as readily may be demonstrated, is a stable compound resulting from the combining action of the formaldehyde with the amino acids of the keratin. This new compound has definite antiseptic properties which remain active in the case of unused and stored brushes over long periods and which were found also to be present in brushes over a year old and in use for about a month. While it is true that to some extent the antiseptic properties are due to some formaldehyde adsorbed on the bristle, nevertheless, it has been demonstrated that upon removal of the adsorbed formaldehyde there was still a very definite antiseptic action by the formaldehydeamino acid compound.

Having described the claimed as new is:

1. Bristlesof marked strength and definite resistance to wet breakdown, comprising natural bristles whose body structure has been chemically altered by reacting the keratin component with an aldehyde at a pH value of more than 3.5 and less than '7.

2. Bristles of marked strength and definite resistance to wet breakdown, comprising natural bristles whose body structure has been chemically altered by reacting the keratin component with an aldehyde at a pH value ranging between 3.5 and 4.5.

3. Natural bristles of marked strength and definite resistance to wet breakdown and char acterized by their water holding capacity, said bristles comprising a stable compound resulting from the combining action of formaldehyde and the amino acid of keratin, the pH value of the formaldehyde being adjusted to between 3.5 and 4.5.

4. The method of treating natural bristles intended for toothbrushes in order to impart added strength and to increase their resistance to wet breakdown which comprises the steps of soaking the bristles in distilled water for a peinvention, what is riod efiective to open them up to easy penetration by a toughening fiuid, removing excess moisture from the bristles, subjecting them to the action of a formaldehyde solution adjusted to a pH value of between 3.5 and 4.5 by the addition of sodium hydroxide for a sufiicient time to cause the formaldehyde to react with the amino acid of the keratin and form a stable compound, and then drying the bristles.

ALBERT A. STONEHUJL. 

